Analysis of Vitamin D Receptor Polymorphisms in Patients with Familial Multiple Sclerosis

A review of the critical role of vitamin D axis on the immune system

In recent years, the physiological and molecular functions of vitamin D (Vit-D) have been deeply investigated. At first, Vit-D was considered a regulator of mineral and skeletal homeostasis. However, due to the extensive-expression pattern of Vit-D receptor (VDR) in almost every non-skeletal cell, Vit-D is considered mainly a multifunctional agent with broad effects on various tissues, notably the immune system. The expression of VDR in immune cells such as dendritic cells, monocyte/macrophage, neutrophils, B cells and T cells has been well demonstrated. Besides, such immune cells are capable of metabolizing the active form of Vit-D which means that it can module the immune system in both paracrine and autocrine manners. Vit-D binding protein (DBP), that regulates the levels and homeostasis of Vit-D, is another key molecule capable of modulating the immune system. Recent studies indicate that dysregulation of Vit-D axis, variations in the DBP and VDR genes, and Vit-D levels might be risk factors for the development of autoimmune disease. Here, the current evidence regarding the role of Vit-D axis on the immune system, as well as its role in the development of autoimmune disease will be clarified. Further insight will be given to those studies that investigated the association between single nucleotide polymorphisms of DBP and VDR genes with autoimmune disease susceptibility.

Association of vitamin D receptor polymorphisms with vitamin D and calcium levels in Turkish multiple sclerosis patients

Aim: The present study was conducted to assess the impact of gene (vitamin D receptor [VDR] polymorphisms) - environment (serum vitamin D and calcium levels) interaction on multiple sclerosis (MS) risk. Materials & methods: FokI, BsmI, TaqI and ApaI genotyping were performed in 149 MS patients and 127 controls. We measured serum vitamin D and calcium levels. Results: No significant difference between VDR polymorphisms and MS risk was detected. In patients with FokI ff, BsmI Bb, TaqI Tt and ApaI AA genotypes, vitamin D levels were statistically higher. Serum calcium levels were significantly lower in patients with FokI FF, Ff, all BsmI and TaqI genotypes and ApaI AA and Aa genotypes. Conclusion: No significant association was found between VDR polymorphisms with MS risk.

ε2 , ε3 , and ε4 variants of ApoE; rs2228570 (VDR), rs4588 and rs7041 (VDBP) polymorphisms in patients with multiple sclerosis: A case-control study in Turkish population

AIM OF THE STUDY

Multiple sclerosis (MS) is a degenerative disease characterized by autoimmune demyelination in the central nervous system. Yet, underlined genetics or environmental markers are still controversial. The impact of vitamin D and cholesterol on disease activity has been phrased by many studies; however, the data available for the Turkish population are very limited. This study aimed to investigate the effect of vitamin D-related polymorphisms (VDBP and VDR) and cholesterol-related variants of ApoE on Turkish MS patients.

MATERIALS AND METHODS

Total DNAs were extracted from peripheral blood samples of 51 MS patients and 50 healthy volunteers. rs4588 and rs7041 polymorphisms of VDBP, rs2228570 of VDR, as well as ε2, ε3, and ε4 variants of ApoE, were investigated by RT-PCR. Biochemical parameters which thought to be associated with MS were also measured. Results were evaluated statistically.

RESULTS

Homozygous mutant genotype and G allele of rs2228570 in VDR, as well as heterozygous genotype of rs4588 in VDBP, were found statistically high in patients. Total cholesterol, triglyceride, and LDL-C levels were found significantly high, whereas HDL-C and vitamin D levels were low in patients. An association was found between rs4588 variation and high triglyceride levels. Similar correlations were found between ε2 genotype and low LDL-C level; ε3 genotype and higher LDL-C. Gender, triglyceride, HDL-C, and AA genotype in rs4588 had a significant effect on MS progression.

CONCLUSION

The variations of rs2228570 and rs4588, vitamin D deficiency, and biological parameters related to cholesterol metabolism may be associated with MS risk.

Gene expression profiles of YAP1, TAZ, CRB3, and VDR in familial and sporadic multiple sclerosis among an Iranian population

Alterations in the regulatory mechanisms that control the process of myelination in the nervous system, may lead to the impaired myelination in the Multiple sclerosis. The Hippo pathway is an important mediator of myelination in the nervous system and might contribute to the pathophysiology of MS. This study examined via qPCR the RNA expression of YAP1, TAZ, and CRB3 as the key effectors of the Hippo pathway and also, VDR in the peripheral blood of 35 sporadic, 37 familial MS patients; and also 34 healthy first-degree relatives of the familial MS patients (HFR) and 40 healthy individuals without a family history of the disease (control). The results showed the increased expression of VDR in the sporadic group, as compared to other groups. There was also an increased expression of TAZ in the familial and HFR groups, as compared to the control group. The familial and sporadic patients displayed a significantly lower level of expression of YAP1 in comparison to the HFR group. The increased expression level in the sporadic patients and control group, as compared to the HFR group, was seen in CRB3. We also assessed different clinical parameters and MRI characteristics of the patients. Overall, these findings suggest that Hippo pathway effectors and also VDR gene may play a potential role in the pathophysiology of the sporadic and familial forms of MS. Confirmation of different gene expression patterns in sporadic and familial MS groups may have obvious implications for the personalization of therapies in the disease.

Assessment of vitamin D-binding protein (DBP) gene polymorphisms and their correlation with multiple sclerosis: a case-control study in a sample of the Syrian population

Background

Vitamin D deficiency is a major health concern as it increases the risk of developing many serious diseases. Recently, the correlation between vitamin D deficiency and multiple sclerosis (MS) is a matter of serious debate. In this case-control study, we aimed to assess the correlation between genetic changes in the vitamin D-binding protein (DBP) gene and their consequence on MS patients. Our sample study consisted of 110 individuals; 40 patients with MS as cases and 70 healthy controls. Vitamin D levels were determined by immunofluorescence assay, and polymorphisms at rs7041 (c.1296 T > G p.Asp416Glu) and rs4588 (c.1307C > A p.Thr420Lys) of the DBP gene were genotyped using PCR/RFLP method for all cases and controls.

Results

Our results showed that genotype frequencies were consistent with Hardy-Weinberg equilibrium. A significant association was found in rs7041 (c.1296TT) homozygous wild-type, and the odds ratio was < 1 suggesting a protective role against developing MS (OR; 0.03, p = 0.0002) whereas the c.1296GG genotype was significantly correlated with an increased risk for MS by 6 folds (OR: 6.0000, p < 0.0001). No significant association was noted at rs4588 and MS occurrence. In addition, our compound genotyping results revealed that haplotypes 1S-1S are 6 times more likely to develop MS, whereas haplotypes 1F-1F had a more protective role in MS patients (OR: 0.063, p = 0.06.), respectively. The risk of vitamin D insufficiency in patients was greater by 14 folds compared to controls (OR: 14.05, p = 0.0128). Furthermore, the c.1296GG genotype was associated significantly by more than 4 times with insufficient levels of vitamin D and by 7 folds with vitamin deficiency.

Conclusions

We conclude that polymorphisms in the DBP gene could have independent effects on the risk of developing multiple sclerosis. The homozygous recessive genotype at rs7041 was associated with insufficient levels of vitamin D and with the risk of MS emergence.

Vitamin D and Genetic Susceptibility to Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disease affecting the central nervous system (CNS), resulting from the interaction among genetic, epigenetic, and environmental factors. Vitamin D is a secosteroid, and its circulating levels are influenced by environment and genetics. In the last decades, research data on the association between MS and vitamin D status led to hypothesize a possible role for hypovitaminosis D as a risk factor for MS. Some gene variants encoding proteins involved in vitamin D metabolism, transport, and function, which are responsible for vitamin D status alterations, have been related to MS susceptibility. This review explores the current literature on the influence of vitamin D-related genes in MS susceptibility, reporting all single-nucleotide polymorphisms (SNPs) investigated to date in 12 vitamin D pathway genes. Among all, the gene codifying vitamin D receptor (VDR) is the most studied. The association between VDR SNPs and MS risk has been reported by many Authors, with a few studies producing opposite results. Other vitamin D-related genes (including DHCR7/NADSYN1, CYP2R1, CYP27A1, CYP3A4, CYP27B1, CYP24A1, Megalin-DAB2-Cubilin, FGF-23, and Klotho) have been less investigated and achieved more conflicting evidence. Taken together, findings from the studies reviewed cannot clarify whether and to what extent vitamin D-related gene variants can influence MS risk.

Environmental Influencers, MicroRNA, and Multiple Sclerosis

Multiple sclerosis (MS) is a complex neurological disorder characterized by an aberrant immune system that affects patients' quality of life. Several environmental factors have previously been proposed to associate with MS pathophysiology, including vitamin D deficiency, Epstein-Barr virus (EBV) infection, and cigarette smoking. These factors may influence cellular molecularity, interfering with cellular proliferation, differentiation, and apoptosis. This review argues that small noncoding RNA named microRNA (miRNA) influences these factors' mode of action. Dysregulation in the miRNAs network may deeply impact cellular hemostasis, thereby possibly resulting in MS pathogenicity. This article represents a literature review and an author's theory of how environmental factors may induce dysregulations in the miRNAs network, which could ultimately affect MS pathogenicity.

Vitamin D and Multiple Sclerosis: An Open-Ended Story

Multiple Sclerosis (MS) is a chronic inflammatory autoimmune disease of the Central Nervous System (CNS). Genetic, epigenetic and environmental factors interact together, contributing to the complex pathogenesis of the disease. In the last decades, the role of hypovitaminosis D on MS risk was hypothesised. Several factors drive the regulation of vitamin D status, including genetics. The current review summarises the literature evidence on the association between vitamin D and MS, with a focus on the genetic polymorphisms in vitamin D-related genes. The variants of the genes codifying Vitamin D Receptor (VDR), Vitamin D Binding Protein (VDBP) and CYP enzymes have been investigated, but the findings are controversial. Only a few studies have addressed the role of DHCR7 polymorphisms in MS risk.

Association between vitamin D receptor (VDR) polymorphisms and the risk of multiple sclerosis (MS): an updated meta-analysis

Background

The association between the Vitamin D Receptor (VDR) gene polymorphism and the risk of Multiple sclerosis (MS) has been evaluated in several researches. However, the findings were inconsistent and inconclusive. Therefore, we set out a meta-analysis of all eligible published case-control studies to obtain an exact evaluation of the association between VDR gene polymorphisms and MS.

Method

All relevant studies reporting the association between the VDR gene FokI (rs2228570), or/and TaqI (rs731236) or/and BsmI (rs1544410) or/and ApaI (rs7975232) polymorphisms and susceptibility to MS published up to May, 2019 were identified by comprehensive systematic search in the electronic database of web of science, Scopus, and PubMed. After that, the strength of association between VDR gene polymorphisms and susceptibility to MS was evaluated by odds ratio (OR) and 95% confidence interval (CI).

Results

A total of 30 case–control studies were included in the meta-analysis. The overall results suggested a significant association between TaqI polymorphism and MS risk under heterozygote genetic model (OR = 1.27, 95%CI = 1.01–1.59, random effect). Moreover, the pooled results of subgroup analysis declined presence of significant association under all defined genetic model. In subgroup analysis, BsmI polymorphisms was associated with increased risk of MS under recessive model in Asian populations. On the other hand, ApaI polymorphism was associated with decreased risk of MS under recessive and aa vs. AA model in Asian populations.

Conclusion

This meta-analysis suggested a significant association between TaqI polymorphism and MS susceptibility. Furthermore, BsmI polymorphism was associated with increased risk of MS in Asian populations. In contrast, ApaI polymorphism was associated with decreased risk of MS in Asian populations. Future large-scale studies on gene–environment and gene–gene interactions are required to estimate risk factors and assist early diagnosis of patients at high risk for MS.

Association of Vitamin D Receptor Gene Polymorphisms and the Risk of Multiple Sclerosis: A Meta Analysis

BACKGROUND

Previous studies have reported vitamin D receptor (VDR) polymorphisms in multiple sclerosis (MS); however, the results remain contradictory. This study aimed to investigate the association between VDR polymorphisms and the risk of MS.

METHODS

PubMed and Embase databases were searched to obtain eligible studies. Data were calculated by odds ratios (OR) with 95% confidence intervals (CI).

RESULTS

Twenty seven case-control studies with 4879 MS patients and 5402 controls were included. There was no significant association between ApaI polymorphisms and MS in the overall population. In Asians, no association was found between ApaI polymorphism and MS in the recessive, dominant, Codominant (OR1), Codominant (OR2), Codominant (OR3) models and allele contrast. Similar results were obtained between BsmI polymorphisms and MS. The association between TaqI polymorphism and MS showed significance in the recessive, homozygous, codominant (OR3) models in the overall population and Caucasians. The dominant model showed no association of Taq I polymorphism with MS risk in HLA-DRB1*15-positive and HLA-DRB1*15-negative groups. FokI polymorphism with MS was found in Codominant (OR3) model in the overall population. In Asians, FokI polymorphism showed association with MS in recessive, dominant, Codominant (OR1), Codominant (OR3) models and allele contrast. Subgroup analysis of sex showed no associations between TaqI or FokI polymorphism and MS risk in males or females in all models or allele contrast.

CONCLUSIONS

The VDR TaqI polymorphisms showed association with MS risk, especially in Caucasians. In Asians, ApaI and FokI polymorphisms correlated with MS risk, while BsmI polymorphisms showed no association with MS.

Exonic variants of genes related to the vitamin D signaling pathway in the families of familial multiple sclerosis using whole-exome next generation sequencing

INTRODUCTION

Vitamin D (VD) deficiency has been associated with multiple sclerosis (MS) and other autoimmune diseases (AIDs). However, the effect of the genetics of VD on the risk of MS is subject to debate. This study focuses on genes linked to the VD signaling pathway in families with MS. The evaluation of gene variants in all the members of families could contribute to an additional knowledge on the information obtained from case-control studies that use nonrelated healthy people.

MATERIAL AND METHODS

We studied 94 individuals from 15 families including at least two patients with MS. We performed whole-exome next generation sequencing on all individuals and analyzed variants of the DHCR7, CYP2R1, CYP3A4, CYP27A1, GC, CYP27B1, LRP2, CUBN, DAB2, FCGR, RXR, VDR, CYP24A1, and PDIA3 genes. We also studied PTH, FGF23, METTL1, METTL21B, and the role of the linkage disequilibrium block on the long arm of chromosome 12, through analysis of the CDK4, TSFM, AGAP2, and AVIL genes. We compared patients with MS, other AIDs and unaffected members from different family types.

RESULTS

The study described the variants in the VD signaling pathway that appear in families with at least two patients with MS. Some infrequent variants were detected in these families, but no significant difference was observed between patients with MS and/or other AIDs and unaffected family members in the frequency of these variants. Variants previously associated with MS in the literature were not observed in these families or were distributed similarly in patients and unaffected family members.

CONCLUSION

The study of genes involved in the VD signaling pathway in families that include more than one patient with MS did not identify any variants that could explain the presence of the disease, suggesting that VD metabolism could probably play a role in MS more as an environmental factor rather than as a genetic factor. Our study also supports the analysis of cases and unaffected individuals within families in order to determine the influence of genetic factors.